Polyarylates are aromatic polyesters derived from dihydric phenols and aromatic dicarboxylic acids. The material based on 2,2-bis(4-hydroxyphenyl)propane (bisphenol-A) and a 50:50 mixture of terephthalic and isophthalic acids (1) is offered commercially by Amoco Performance Products, Inc. under ##STR1## the tradename of ARDEL D-100.RTM.. Polyarylates are high temperature, high performance thermoplastic polymers with a good combination of thermal and mechanical properties. They display excellent UV resistance and have good processability which allows them to be molded into a variety of articles.
Polyarylates are high modulus, rigid thermoplastics; the incorporation of their outstanding properties into thermoplastic elastomers would be of great practical and scientific interest. It was now unexpectedly discovered that polyarylates having one terminal dihydroarylcyclobutene group per chain, react with unsaturated, low Tg polymers to give elastomeric materials displaying a combination of excellent mechanical and thermal properties. The scope of the reaction is outlined in the following section.
Polymers based on dihydroarylcyclobutenes have been mentioned in the literature. Thus, U.S. Pat. No. 4,540,763 describes the formation of thermosets by thermally reacting poly(dihydroarylcyclobutenes). Thermosetting materials may be formed via a similar reaction from bifunctional dihydrobenzocyclobutene-alkyne imide monomers, as shown in U.S. Pat. No. 4,675,370 and in the Journal of Polymer Sci., Polymer Chemistry 25, p. 3159 (1987); a related reaction, the formation of thermosetting polymers by heat-treating alkynyl-bridged poly(dihydroarylcyclobutenes), is claimed in U.S. Pat. No. 4,687,823. The formation of crosslinked products is also the subject of U.S. Pat. Nos. 4,687,815 and 4,708,994. Dihydrobenzocyclobutene end-capped styrene, diene, or styrenediene copolymers were shown to be capable of thermally induced coupling--see U.S. Pat. No. 4,708,990. Difunctional dihydroarylcyclobutenes, such as the 4,4'-ethylidene dihydrodibenzocyclobutene, were used successfully as crosslinking agents for ethylene-propylene-diene rubbers, as described in European Patent Application No. 227,163. Remarkably, however, there are no references teaching the use of dihydroarylcyclobutene chemistry for the preparation of thermoplastic graft copolymers.